Sacabambaspis – Late Ordovician (470-453 Ma)Today we’re talking about something really c

Sacabambaspis – Late Ordovician (470-453 Ma)Today we’re talking about something really cute. It’s an ancient, primitive fish with an adorable face. It’s Sacabambaspis!What we’re looking at is an early jawless fish. Fish in the Ordivician period were small, simple little guys. Usually tubes with eyes and sometimes armor. Most of them didn’t even have fins, so a lot of them, including Sacabambaspis, look a lot like armor-plated tadpoles. It’s hard to imagine a world where fish don’t dominate the oceans, but that’s just how it was during the Ordovician. These guys, as well as their relatives, lived in the shadow of larger invertebrates, still enjoying the twilight of their rule that began during the Cambrian period. Sacabambaspis was a bottom-dweller. Its mouth was pretty much just a circle in structure, but the inside was lined with bony plates that aided in suction feeding as it slurped bits of nutrients off the seafloor. Its eyes were square in the front of its head, giving it an adorable face. It’s like a little submarine, I just wanna hug it! Bony plates covered its gills and the front half of its body. There’s also evidence of a feature found in most modern fish called the lateral line. This is an organ system that lets fish sense the flow of water. There isn’t really an analogue in terrestrial vertebrates, but if I had to say one, it’s kind of like our sense of hearing. Kind of.Although Agnatha (the technical name for jawless fishes) are the oldest group of fish, Sacabambaspis likely lived at the same time as early jawed fishes (Gnathostomata). This was still the primetime for jawless fishes, though. It would be a while before their jawed counterparts became more successful. So much more successful, in fact, that there are only two groups of agnathans alive today: lampreys and hagfish. Also, a fun fact about Gnathostomata is that the technical definition includes all vertebrates with jaws. So, you and I, and your dog, and my cat, are jawed fishes.Don’t let all this talk of fish living in the shadows of bigger animals convince you that fish were underdogs or barely eking out their existence back then. It’s easy to try and fit the history of life into a sort of poetry, where the fish struggled along until given the chance to rise up and take over. That wasn’t really the case, though. Fish were thriving in the lower niches of the food web during this time. You wouldn’t call rodents underdogs today, just because none of them are apex predators in their ecosystems. Fish were similar; they were all over the place and lived all kinds of different lives. Considering what we know about the Ordivician fish, it’s not hard to see why they jumped at the opportunity to dominate the seas once the extinction event at the end of the period wiped out everything else. We like to think fish are dumb and primitive, but they have a spectacularly well-adapted body plan for aquatic life. They’re great at being animals, and I am ready to fight anyone who disagrees. -- source link

More pics about